G. J. Mattey’s Notes on Hume’s Treatise, Book I, Part III, Section 4

Notes on Hume’s Treatise

by G. J. Mattey

Book 1
Of the UNDERSTANDING
PART 3
Of knowledge and probability.

Sect. 5. Of the impressions of sense and memory.

The search for the nature of the relation of causation has led the author to investigate how we make inferences from cause to effect or from effect to cause. In the previous section, he had argued that such inferences always begin with either impressions or with ideas of memory, the latter being “equivalent to impressions” (Section 4) and here sometimes just called “impressions.” In this section, he discusses the nature of the impressions of sense and the ideas of memory with which causal inference must begin.

The author in paragraph 2 holds that the origin of impressions of sense is unknown. He cites three possible sources of such impressions. This range of possibilities is found in Descartes’s Sixth Meditation. Descartes argued that what the author calls “impressions of sense” originate with extended objects. Berkeley, in Principles of Human Knowledge, sections 26-30, presented the same options and claimed that God is their cause. Regarding memory, Locke’s Essay, Book II, Chapter X, entitled “Of Retention,” contains a detailed discussion of the mechanisms of memory. Locke claimed, contrary to the author, that in memory, perceptions are revived and are accompanied with a new perception, that the mind has had them before.

1. In our causal reasoning, we consider objects that produce objects or that are produced by objects. We begin with impressions of sense or memory and relate such impressions to the idea of the object that produces or is produced. Thus, the two perceptions involved in the inference are “of a mix’d and heterogeneous nature,” so much so that they are “essentially different from each other.” As a result, three things must be explained in the account of causal reasoning:

2. The ultimate cause of impressions of sense is regarded by the author as being “perfectly inexplicable by human reason.” Sense impressions may have their origins in sensible objects, be created by the human mind itself, or be produced in us by God. But in the present case, the origin of sense impressions is of no consequence. All that is needed for us to draw inferences from them is that they be coherent, “whether they be true or false; whether they represent nature justly, or be mere illusions of the senses.”

3. Having laid down coherence as the only relevant feature of the impressions, the author turns to the ideas of memory. [Here, there is a problem that does not arise for impressions, namely, that the ideas of memory are very similar to those of imagination, but we do not make causal inferences from what we merely imagine.] There can be nothing in the [production of] simple ideas of memory and imagination that distinguishes them, since both are derived from impressions and cannot “go beyond these original perceptions.” Nor can the arrangement of complex ideas be the source of the distinction. Although memory preserves order and imagination is free, this quality cannot be used to distinguish them. To do so, we would have to reproduce the original impressions and compare their order with the order of the present ideas. If this could be done, we could ideas preserve the original order and which do not. But this cannot be done; all perceptions of memory are ideas, which are only copies of impressions. So, neither the order of complex ideas nor the nature of simple ideas suffices to distinguish ideas of memory from those of imagination. The author claims that it “follows” from this that it is the “superior force and vivacity“ of the ideas of memory that differentiate them from those of the imagination. Without this difference, we would be unable to separate our fantasies from our rememberances of what really took place.

4. [Appendix. The author illustrates his point with an example of two friends who witnessed the same event. One of them, A, remembers it, while the other, B, forgets it. A has a chain of ideas in his mind, and when he recounts the event to B, B forms a similar chain. However, B still regards the sequence of ideas as the product of A’s imagination. Then A finally recounts a feature of the event that causes B to change his mind and think that he remembers it. The difference in the ideas before and after is not in their order, but only in their vivacity. Because the ideas feel different, they are regarded as memories.

5. Since the only difference between B’s ideas before and after his memory has been jogged is that they feel different, it can be asked what the difference in feeling is. The author thinks that everyone will agree that it is a difference in force and vivacity.] The author now considers how the strength and vivacity of memory weaken over time. A painter who wants to depict a certain emotion in the subject of his painting will try to observe someone with that emotion. This will enliven his own ideas beyond what the imagination can do. At first, the idea of memory is strong, but it then weakens to the point where its force almost, if not entirely, disappears. The result of this weakening is that we often have difficulty determining whether we are remembering something or merely imagining it. “I think I remember such an event, says one; but am not sure. A long tract of time has almost worn it out of my memory, and leaves me uncertain whether or not it be the pure offspring of my fancy.”

6. The opposite effect can be found in certain cases: an idea of imagination may become enlivened to the point that it is taken for an idea of memory. The author cites liars, who originally recognize that their lies are a product of their imagination, but who repeat the lies so often that they begin to believe that what they have said actually happened. Whereas the weakening effect described in the last paragraph is the work of nature, the strengthening effect is a product of custom and habit. The author notes that this is only one of many ways in which custom and habit influence our ideas.

7. The author concludes the section with an important inference. It has been established that the strength and vivacity of ideas of memory is what distinguishes them from ideas of the imagination. Accompanying ideas of memory are “belief or assent,” [as with the cases of the person whose memory is jogged and of the liar]. It then “appears” that belief just is a strong and vivid idea. “To believe is in this case to feel an immediate impression of the senses, or a repetition of that impression in the memory.” If a belief is a strong and lively idea, then the impression of sense or idea of memory with which causal inference begin constitutes a belief that is the basis of a causal inference. The original perception, then, “lays the foundation of that reasoning, which we build upon it, when we trace the relation of cause and effect.”

The problem of discovering the origin of sense impressions is treated in Section 12, paragraph 11. “By what argument can it be proved, that the perceptions of the mind must be caused by external objects, entirely different from them, though resembling them (if that be possible) and could not arise either from the energy of the mind itself, or from the suggestion of some invisible and unknown spirit, or from some other cause still more unknown to us?” In Section 5, the memory and senses are treated only as the starting point for belief, and the distinction between memory and imagination is not explicitly drawn.